1. Field of the Invention
The present invention relates generally to microwavable containers for food products and apparatus and methods of making the same, and, more particularly, to apparatus and methods for making a microwavable tub for storing, shipping, heating and serving food products.
2. Description of Related Art
The increasing popularity of microwave cooking has lead to the development of several types of containers for microwave heating of food products. For example, a number of bag-type containers for microwave popping of popcorn are available. These containers are typically formed of paper or other flexible materials, and often include heating elements of microwave interactive susceptor material that absorb microwave energy to generate heat, which pops the popcorn. Such containers are typically shipped and stored in a folded configuration and, upon heating and popping of the corn, unfold into an expanded configuration.
More rigid containers have also been developed, such as cup-shaped containers for microwave heating of popcorn. These containers typically are in the form of generally frustoconical paperboard tubs. A microwave susceptor is installed on or around the floor of the tub and a quantity of unpopped corn and cooking oil or shortening is placed in the tub's interior. A plastic film or other barrier material is often applied over the corn in an effort to seal out external contaminants, seal in moisture, and preserve freshness. Morever, it has been found that moisture loss from popcorn inhibits popping and reduces popped volume.
Efforts to form a hermetic seal around the food product in previously known containers have proven less than fully satisfactory. One known container provides a concave cooking tray formed of coated paperboard stock for containing the food product and heating through microwave absorption. The tray includes a number of folds or corrugations, which present discontinuities in any seal attempted to be formed with a barrier material. These discontinuities form air channels that allow moisture loss from the food product. In an attempt to overcome this problem, a moisture impervious liner has been provided around the exterior of the tray, which liner is sealed to the barrier film around the lip of the tray. The multiple components required in previously known containers, however, typically results in increased costs of materials and assembly. Another disadvantage found to inhere in previously known containers incorporating a tray for containing the food product is the potential for the food product to be displaced inadvertently from the tray onto the shelf or ledge formed by the lip of the tray, removing the food product from thermal contact with the microwave susceptor material, often resulting in incomplete cooking or popping.
Previously known paperboard tub containers for microwave cooking are typically assembled by depositing the food product onto the floor of an upright container, or into a heating tray placed within the container, and then installing liners and/or film in various configurations in an attempt to form a seal around the food product. As discussed above, the provision of cooking trays and liners undesirably increases expense and may adversely affect cooking performance. If the food product is distributed across the container floor, attempts to form a seal around the food product by sealing a cover film to the container walls typically are unsuccessful, as moisture may escape through the walls and floor of the container, and/or through the seam between the walls and floor.
Thus, there is a need for a container for microwave cooking of food products, which overcomes disadvantages of previously known containers. A need further exists for an economical and efficient method and apparatus of making such a microwavable container for food.